Evaluation of the Rotating-Frame Relaxation (T_1ρ) Filter and Its Application in Metabolomics as an Alternative to the Transverse Relaxation (T₂) Filter

Abstract

Nuclear magnetic resonance (NMR)-based metabolomic studies commonly involve the use of T 2 filter pulse sequences to eliminate or attenuate the broad signals from large molecules and improve spectral resolution. In this paper, we demonstrate that the T 1ρ filter-based pulse sequence represents an interesting alternative because it allows the stability and the reproducibility needed for statistical analysis. The integrity of the samples and the stability of the instruments were assessed for different filter durations and amplitudes. We showed that the T 1ρ filter pulse sequence did not induce sample overheating for a filter duration of up to 500 ms. The reproducibility was evaluated and compared with the T 2 filter in serum and liver samples. The implementation is relatively simple and provides the same statistical and analytical results as those obtained with the standard filters. Regarding tissues analysis, because the duration of the filter is the same as that of the spin-lock, the synchronization of the echo delays with the magic angle spinning (MAS) rate is no longer necessary as for T 2 filter-based sequences. The results presented in this article aim at establishing a new protocol to improve metabolomic studies and pave the way for future developments on T 1ρ alternative filters, in liquid and HR-MAS NMR experiments.

In-Cell Structural Biology by NMR: The Benefits of the Atomic Scale

“…587,588 Lower strengths might provoke offset and relaxation-dispersion effects. 589 Interestingly, T1ρ filters could be much longer, up to 500 ms, and thus more efficient without any sample heating, as shown recently. 589 NMR metabolomics use T2 filters to remove signals from plasma macromolecules for example.…”

“…589 Interestingly, T1ρ filters could be much longer, up to 500 ms, and thus more efficient without any sample heating, as shown recently. 589 NMR metabolomics use T2 filters to remove signals from plasma macromolecules for example. 590 The T2 filter has indeed been shown to provoke faster relaxation of macromolecules than the T1ρ filter, and thus a more efficient background removal.…”

“…T1ρ filters of a few tens of milliseconds are usually applied, which is sometimes not enough to remove signals from abundant cellular species like lipids. On-cell NMR reports were not very explicit about the strength of the applied T1ρ spin-lock, but it has usually a strength (γ/2π) B 1 ∼ 5 kHz. , Lower strengths might provoke offset and relaxation-dispersion effects . Interestingly, T1ρ filters could be much longer, up to 500 ms, and thus more efficient without any sample heating, as shown recently .…”

“…On-cell NMR reports were not very explicit about the strength of the applied T1ρ spin-lock, but it has usually a strength (γ/2π) B 1 ∼ 5 kHz. , Lower strengths might provoke offset and relaxation-dispersion effects . Interestingly, T1ρ filters could be much longer, up to 500 ms, and thus more efficient without any sample heating, as shown recently . NMR metabolomics use T2 filters to remove signals from plasma macromolecules for example .…”

Monitoring Drug–Protein Interactions in the Bacterial Periplasm by Solution Nuclear Magnetic Resonance Spectroscopy

“…While small molecules, such as β-lactams, are suitable targets for such an NMR study, other cell components can negatively impact the quality of the spectrum, by contributing with broad and overlapping signals. To overcome this problem, we employed the T 1ρ filtering method, which separates the present molecular species based on their transversal relaxation rates . As a result, broadened NMR signals of high molecular weight molecules are largely suppressed, whereas those from small molecules, such as mecillinam, are mostly retained.…”